1. Field of the Invention
The present invention relates generally to releasing filament wound tubes from a mandrel, and more particularly to an apparatus and method for releasing a filament wound tube from a mandrel employing a removable fiber.
2. Description of the Related Art
Filament wound tubes are fabricated by winding a fiber around an axisymmetric rotating mandrel in a predetermined manner. The fiber is guided onto the mandrel using roller guides that are moved back and forth axially along the mandrel as is well known in the art. By coordinating the positions of the guides and mandrel, it is possible to wind a geometric pattern with the fiber oriented in a specific direction.
Because of friction between the mandrel and the tube, it is not possible to remove the tube from the mandrel unless some type of slippage plane exists therebetween. Attempts to force a tube off a mandrel typically cause significant damage to the tube.
One prior art approach of releasing a filament wound tube from a mandrel is to coat the mandrel with a lubricant containing spray. This approach is successful with short tubes having small diameters such as about six inches long and about one and a half inches in diameter.
Another prior art approach employs the use of collapsible or semi-collapsible mandrels. The mandrels are disassembled fully or partially and withdrawn from the completed filament wound tube. Ordinarily these devices are expensive particularly when their shape is complex.
Still other prior art approaches use tubes or covers for the mandrel such as cardboard tubes or wrapping the mandrel with multiple layers of a wrap made from plastic or polytetrafluoroethylene to create a slippatge plane. Experience has shown that long tubes, for example, twenty-four (24) inches or longer cannot be slipped off a mandrel even when three layers of a plastic wrap is applied.
Thus, there is a need for an apparatus and method for releasing a filament wound tube from a mandrel that allows short or long tubes to be easily removed from a mandrel without damage to the tube. The method and apparatus should be inexpensive, easy to use, and reliable.